1. Field of the Invention
The present invention relates to a gas safety device. In particular, the present invention relates to a gas safety device including a main body and a ball that can block a gas passageway defined by a longitudinal through-hole of the main body when excessive flow occurs, thereby preventing mass leakage.
2. Description of the Related Art
Pressure difference has already been utilized in gas safety devices for assuring safety use of gas. U.S. Pat. No. 5,983,928 discloses a gas safety valve comprising a valve body with a longitudinal through-hole for receiving a ball. The longitudinal through-hole of the gas safety valve comprises several sections of various inner diameters such that when mass leakage occurs, the ball is moved to compress a spring and to block the longitudinal through-hole as a result of a pressure difference between two sides of the ball. Such a structure can be applied to gas sources of different pressure by means of simply changing the spring. However, the elastic constant of springs cannot be always identical even if they are manufactured under the same condition and thus fail to meet the requirement of precision. Namely, the ball might be incapable of blocking the longitudinal through-hole of the valve body, as the elastic constant of the spring is not within the predetermined operational range.
U.S. Pat. No. 6,405,751 discloses a gas safety valve comprising a main body, a valve seat, a restraining member, and an engaging member. The valve seat and the restraining member are threadedly engaged in the main body. The valve seat includes a valve block, a spring, and an adjusting element. When gas leakage occurs, the valve block blocks a longitudinal through-hole of the valve body, preventing mass leakage. Operation of the gas safety valve can be precisely achieved within a predetermined operational range. The structure of this gas safety valve is, however, complicated. When adjustment is required, the valve seat and the restraining member have to be troublesomely removed from the main body. And the valve seat and the restraining member have to be threadedly reengaged in the main body. As a result, the precision after adjustment may still has an error.